The invention relates to an adjustable steering column for a motor vehicle with a clamping mechanism in the opened state of which the steering column is adjustable and in the closed state of which the set position of the steering column is fixed. The clamping mechanism comprises an actuating lever and a clamp element, which, for opening and closing the clamping mechanism, is rotatable by the actuating lever about an axis of rotation.
Adjustable steering columns are known in various embodiments. To secure the adjustment in position in the closed state of the clamping mechanism can be provided, for example, friction faces tightened together by the clamping mechanism for the force-closure securement or toothings, brought together by the clamping mechanism for the form-closure securement. The adjustability can refer to the axial direction of the steering column and/or the inclination adjustment or height direction.
To improve the protection of the motor vehicle driver in the event of a motor vehicle crash, in particular against an impact of the knee on the operating lever of the fixing device, WO 03/018384 A1 has already proposed to realize the operating lever as a deformation element such that it is deformable through an impact with the consumption of energy. For this purpose the operating lever is preferably provided with a specified buckling point. The force leading to the deformation of the operating lever must herein be selected of adequate magnitude in order to exclude deformation during normal operation. The operating lever must further be realized with appropriate geometry in order for a deformation of the operating lever to result due to an impact force acting in the direction toward the motor vehicle front in the event of a crash.
DE 10 141 551 A1 furthermore discloses an adjustable steering column in which a lever part of the operating lever is connected with a bearing part via a tear-off mechanism, through which the lever part can become detached from the bearing part in the event of a crash. The embodiment depicted in this document is relatively complex. It is also necessary to prevent the lever part of the operating lever from becoming unintentionally detached from the bearing part, for example in the presence of an unintentional jolting or improperly applied forces, also in the transverse direction.
U.S. Pat. No. 7,125,046 B2 discloses an adjustable steering column in which, in the event of a crash, the jacket tube can become dislocated in the direction toward the motor vehicle front. Herein, the fastening lever for the lock mechanism is also moved toward the front end of the motor vehicle whereby the knee protection of the driver is said to be improved.